1. Field of the Invention
The invention relates to an art adopted in an exhaust passage of an internal combustion engine mounted on a vehicle to detect an amount of a particulate matter (PM) present in exhaust gas.
2. Description of Related Art
Conventionally, the amount of a particulate matter (PM) present in exhaust gas is be detected using a method that employs a sensor that includes an oxidation catalyst, a heater that heats the oxidation catalyst, and a temperature sensor that detects the temperature of the oxidation catalyst (e.g., see Japanese Patent Application Publication No. 2008-261322 (JP-A-2008-261322).
The references cited above use the amount of heat generated during the oxidization of the particulate matter collected by or deposited on the oxidation catalyst as a parameter. The related art aims at specifying the amount of the particulate matter collected by or deposited on the oxidation catalyst.
However, recent progress in exhaust gas purification has led to reductions in the diameter of particulate matter discharged from the internal combustion engine. Particularly when the detection device is arranged in the exhaust passage downstream of a particulate filter, the diameter of particulate matter leaking from the particulate matter is reduced.
Consequently, the oxidation catalyst may trap less than all the particulate matter in exhaust gas. In this case, the amount of particulate matter present in exhaust gas and the amount of the particulate matter collected by the oxidation catalyst are not closely correlated with each other. Thus, the accuracy in detecting the amount of the particulate matter decreases.